Century Bog Ecological Risk Assessment and Restoration

Princeton Hydro was hired by the Massachusetts Division of Ecological Restoration in 2011 to design and implement a feasibility study for the restoration of a Century Bog in Massachusetts. Century Bog is a 100+ year-old, 60-acre operating cranberry farm that spans the headwaters reach of Red Brook. As part of the study, Princeton Hydro undertook an ecological risk assessment to determine whether decades of pesticide use had created unacceptable risks for wildlife under existing or proposed conditions.

Three broad project objectives were defined for the project as follows:

1. Reduce water temperatures conveyed through the site to Red Brook
2. Facilitate bi-directional passage of river herring through the site
3. Replace the mono-specific cranberry crop and related features (e.g., service roads, dikes, ditches, borrow areas) with native plant communities.

Princeton Hydro evaluated soil and sediment tests performed by others and concluded that historic pesticide residues, especially dieldrin and DDT, disproportionately occurred in a sand cap layer applied across the plantation surface to facilitate cranberry production. Then, the project team designed and implemented a series of subsequent investigations to determine the aqueous mobility of historic pesticides, to assess whether base-level food chain taxa showed evidence of pesticide in their tissue, and to calculate dietary exposure to wildlife that are known to forage this site.

Following completion of the assessment, Princeton Hydro was subsequently retained for engineering design of the restoration project. The ecological risk assessment findings were integrated into our restoration design to reduce the mass of historic pesticide residue available in near-surface soils.

The restoration design included the following:

• Re-naturalizing the cranberry plantation into a native wetland/riparian mosaic of plant community types
• Restoring the Red Brook stream channel in manners that enable passage by river herring while simultaneously lowering stream temperatures
• Establishing a stable, non-eroding stream that reduces exports of fine sediment and nutrients to lower portions of Red Brook